This application incorporates herein by reference in its entirety the disclosures of U.S. Pat. No. 7,403,860, issued Jul. 22, 2008, and U.S. Published Application No. 2006/0169039, published Aug. 3, 2006.
Fueling environments typically store fuel in large storage tanks located beneath the ground, sometimes referred to as “underground storage tanks” (UST). To comply with environmental laws, rules, and regulations, these storage tanks may be double-walled and equipped with various leak detection sensors and inventory reconciliation systems. One popular leak detection sensor is sold by Veeder-Root Company of 125 Powder Forest Drive, Simsbury, Conn. 06070, the assignee of the present application, under the name “The MAG Plus Inventory Measurement Probe” (MAG PROBE™). This probe is typically matched with a tank monitor, such as the TLS-350R, also sold by Veeder-Root Company. Such probes measure a height of fuel within the storage tank and may optionally measure a height of water (if present). The measurements are reported to the tank monitor for usage by the operator of the fueling environment to evaluate and reconcile fuel inventory and/or detect leaks, as is well understood.
The use of anhydrous ethanol (hereafter “ethanol”) as an additive to gasoline is widespread in many countries throughout the world. In particular, 10% ethanol additive (E10) is very popular in the United States. While water separates from plain gasoline, thereby forming a water-fuel interface 34 (FIG. 1), the addition of ethanol allows the fuel, in the instant case E10, to absorb water in a substantially homogenous manner up to approximately 0.4% in suspension, the percentage being dependent on fuel type and temperature. Above 0.4%, the fuel mixture separates into a lower layer 37a and an upper layer 37b (FIGS. 1 and 2), each containing different concentrations of gasoline, ethanol and water. This separation into two distinct layers is referred to as “phase separation”. The mixture of lower layer 37a has a higher density and contains larger percentages of ethanol and water than upper layer 37b. Most automobiles are designed to operate with up to 10% ethanol, but the higher percentages of ethanol and water in lower layer 37a can damage E10 rated equipment. A secondary effect is the depletion of ethanol from upper layer 37b which decreases the octane rating of the fuel and can cause poor performance in automobile engines. A tertiary effect is the potential damage to the tank and other associated equipment due to the corrosive mixture of water and ethanol.
Typically, underground storage tanks use a submersible turbine pump (STP) which draws fuel from approximately six (6) inches from the bottom of the tank. If phase separation occurs and the height of the phase separation boundary 37 between lower layer 37a and upper layer 37b is above the STP inlet, automobiles and other equipment can be exposed to non-compliant fuels.